Boat mover for semiconductor fusion process

ABSTRACT

An arrangement for moving a boat carrying semiconductor wafers through a diffusion furnace is provided wherein the boat is supported free of the walls of the furnace while being moved therethrough, whereby damage to the wafers caused by sudden stops and starts of the boat is avoided.

United States Patent [1 1 Henebry et al.

[ 11 3,744,650 51 July- 10, 1973 BOAT MOVER FOR SEMICONDUCTOR FUSION PROCESS [75] inventors: Thomas F. Henebry, Phoenix, Ariz.;

Sandtord Platter, Bolton, Mass.

[73] Assignee: Semiconductor Electronic Memories Incorporated, Phoenix, Ariz;

[22} Filed: Oct. 26, 1971 [21] Appl. No.: 192,051

[52] US. Cl 214/23, 432/239, 432/259 [51] Int. Cl. F27d 5/00 [58] Field of Search 263/47, 48, 41, 42,

[56] References Cited 7 UNITED STATES PATENTS 3,669,431 6/1972 Lenssetal 263/47R 3,294,261 12/1966 Cloutier, Jr. ..263/6R 1,858,499 5/1932 Hathaway et al. 263/6 R 2,632,839 3/1953 Reynolds 263/6 R Primary Examiner-John J. Camby Assistant Examiner-Henry C. Yuen Attorney-Lindenberg, Freilich & Wasserman 57 ABSTRACT An arrangement for moving a boat carrying semiconductor wafers through a diffusion furnace is provided wherein the boat is supported free of the walls of the furnace while being moved therethrough, whereby damage to the wafers caused by sudden stops and starts of the boat is avoided. I

5 Claims, 1 Drawing Figure PATENTEWWW 3.744.650

nvvwrops SANFORD PLATTER THOMAS F. HENEBRY FIELD OF THE INVENTION This invention relates to apparatus employed with furnaces for heat treatment of semiconductor material and more particularly to improvements therein.

As part of the processing of semiconductor wafers, they are moved into a diffusion oven at a particular rate wherein they are gradually heated up to a temperature above their plastic deformation temperature, and then are moved out of the oven. The rate is usually a slow one being on the order of from 2 to 5 inches per minute. The diffusion oven usually has a central tube into which the boat filled with wafers is moved for heat processing and from which it is thereafter removed.

In many diffusion processes reaction gases produced by the heating causes the inner surface of the diffusion oven tube over which the boat is slid, to be sticky. When a boat is moved in such a furnace, while being supported by the tube, the action of the sticky surface will cause the boat to jerk with the result that a high stress is applied to the wafers at the points where they are supported by the boat. The wafers are normally supported on edge in order to increase the through-put. Because the wafer temperature is above the plastic temperature, in most diffusion furnaces, this jerky motion results in crystal damage and unwanted electrical characteristics causing a high number of rejects or unusable circuits to occur on a chip.

OBJECTS AND SUMMARY OF THE INVENTION An object of this invention is to provide an arrangement for moving a boat into and out of a diffusion furnace smoothly and uninterruptedly.

Yet, another object of the invention is to provide an arrangement for supporting a boat which is moved into and out of a diffusion furnace to eliminate possible damage as a result of boat motion; These and other objects of the invention are provided by an arrangement wherein the boat is supported by a rod free and clear of the furnace walls, whereby it can be moved into and out of the tube smoothly. Thereby possible crystal damage and unwanted electrical characteristics which occur when the boat is pushed along the diffusion furnace walls are eliminated.

The novel features of the invention are set forth with particularity in the appended claims. The invention will best be understood from the following description when read in conjunction with the accompanying drawing which is a view in perspective of an embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The FIGURE shows a view of an embodiment of the invention, drawn in perspective.

A tube represents the central tube of a diffusion furnace. The rest of the furnace is not shown since it is not required for an understanding of the invention. In accordance with this invention, a boat 12, which may be seen in an opening in the tube 10, which is made for the purpose of illustrating the boat position therein, is supported by a rod 14. The boat 12 effectively is made of three quartz rods which are notched for the purpose of supporting exemplary spaced wafers, 16, 18, therein.

It will be appreciated that the two wafers shown are representative of a plurality of wafers which are supported in the boat. The wafers are supported on end to increase production.

The rod 14 may be also a tube, if the material of which the rod is made has sufficient stiffness. With a semiconductor diffusion process, both the boat and tube 14 are preferably made of quartz, since this is an inert material. However, in the heat treatment of other materials possibly other inert materials may be em-,

ployed.

The tube 14 is supported on three guide wheels re spectively 20, 22, and 24. These are positioned beneath and above the tube in order to support it, A spring bias is applied to the guide 22 by means of spring 26, which is connected from the support bed to an axle 30 extending from the guide 22. The axle is supported within a level 32. A rod 34 supports the other end of the lever and extends to a flange 36 which is at right angles to the support bed 28.

The guide 24 is supported by an axle 40, which in turn also extends from the right angle flange 36.

The guide 20 is supported on an axle 42. The axle 42 extends and is supported in the rightangle flange 36. A second axle 44 extends from the guide 20 to engage a pulley 48. A pulley is rotatably driven by a belt 50. The belt is driven by a motor 52. The motor is supported on the support bed 28. i i

The rod or tube 14 supports the boat out of contact with the furnace walls and therefore, the boat with its load of semiconductor wafers can be moved smoothly into and out of the furnace tube without causing any damage.

The roller guide 22, which is on top of the tube is loaded so that the tube and the boat will stay on the center line defined by the tube bottom roller guides respectively 20, 24, throughout the entire movement. The two bottom guides can be adjusted in space so that the center line defined by them is the same as the center line of the furnace tube. The rod 14 must be of such stiffness that the deflection caused by the boat, due to its weight, when in the extended position, is negligible,

There has accordingly been described and shown herein a novel, and useful arrangement for moving a boat through a diffusion furnace in a manner so that damage to the contents thereof is avoided.

What is claimed is:

1. In a system for heat treating semiconductor material which is supported in a boat which is moved through a diffusion furnace, the improvement comprismeans for supporting and moving said boat through said furnace free of all structures including the walls of said furnace,said means extending from within said furnace to the outside during the entire motion of said boat.

2. In a system for heat treating semiconductor material which is supported in a boat which is moved through a diffusion furnace, the improvement comprismg:

a rod or tube supporting and moving said boat within said furnace free of all structures including the furnace walls throughout the entire motion of said boat, and

means for movably supporting said rod outside of said furnace.

3. Apparatus as recited in claim 2 wherein said means for rollably supporting said rod outside of said furnace includes at least three roller guides, two of said roller guides being positioned underneath said rod and the third of said roller guides being positioned on top of said rod between the locations of said other two guides,

and 5 means for yieldably biasing said third roller guide against said rod.

and said rod are made of quartz.

=a= a: a: 

1. In a system for heat treating semiconductor material which is supported in a boat which is moved through a diffusion furnace, the improvement comprising: means for supporting and moving said boat through said furnace free of all structures including the walls of said furnace, said means extending from within said furnace to the outside during the entire motion of said boat.
 2. In a system for heat treating semiconductor material which is supported in a boat which is moved through a diffusion furnace, the improvement comprising: a rod or tube supporting and moving said boat within said furnace free of all structures including the furnace walls throughout the entire motion of said boat, and means for movably supporting said rod outside of said furnace.
 3. Apparatus as recited in claim 2 wherein said means for rollably supporting said rod outside of said furnace includes at least three roller guides, two of said roller guides being positioned underneath said rod and the third of said roller guides being positioned on top of said rod between the locations of said other two guides, and means for yieldably biasing said third roller guide against said rod.
 4. Apparatus as recited in claim 3 including means for rotating one of said roller guides which is beneath said rod.
 5. Apparatus as recited in claim 2 wherein said boat and said rod are made of quartz. 